At present, according to Wheatstone electric bridge principle, tire pressure monitoring systems (TMPS) are widely used in various kinds of vehicles to precisely and promptly monitor air pressure and temperature in vehicle tires.
However, the conventional TMPS generally needs to operate under very strict working conditions. Monitoring of air pressure and temperature in the vehicle tires is realized via an air pressure sensor and a temperature sensor, respectively. Typically, the air pressure sensor and the temperature sensor must be powered continuously. Otherwise, they may lose their basic role of monitoring. After long time of electrification, lifespan of battery in the TMPS is considerably shortened and the TMPS itself may potentially warn mistakenly.
Conventional mechanical or electrical air pressure sensors generally define a chamber therein, and the chamber must be strictly vacuum-pumped. After the air pressure sensor works at high or low temperatures or under humidity for some time, air volume in the chamber will change, which may accordingly lead to a linkage mechanism of the air pressure sensor to move and induce malfunction of the air pressure sensor.
Actually, it is very difficult to set the chamber in perfect vacuum. Even if the vacuum degree in the chamber is reasonably high, the air from the atmosphere still can penetrate the surface of the vehicle tire and enter the chamber, which will inevitably lead to the chamber be filled with air gradually. Therefore, as long as the air pressure sensor's work relies on the vacuum degree of the chamber, the performance of the air pressure sensor will deteriorate consequentially and lifespan of the air pressure sensor will be shortened accordingly. In other words, performance of the vehicle tire warning system is directly determined by the lifespan of the battery and the vacuum degree in the air pressure sensor.
What is needed, therefore, is to provide a vehicle tire warning system which can promptly monitor the air pressure and the temperature in the vehicle tires.